JP2017115204A - Aluminum-based porous body and manufacturing method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aluminum-based porous body suppressing aggregation of molten aluminum or molten aluminum alloy and low in pressure loss of a fluid which flows in a porous body.SOLUTION: There is provided three-dimensional network structure having a three-dimensionally connected skeleton and a pores three-dimensionally communicated by the skeleton, wherein the skeleton consists of aluminum or an aluminum alloy, size of an almost spherical metal lump consisting of the molten aluminum or the molten aluminum alloy blocking communication holes of the structure is 4.0 mm or less in long diameter and porosity is 95% or more.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a porous metal body having a three-dimensional network structure having a skeleton that is three-dimensionally connected and having communication holes that communicate with each other in a three-dimensional manner.

  A metal porous body having a three-dimensional network structure having a three-dimensionally connected skeleton and three-dimensional communication holes formed by the skeleton is obtained by conducting a conductive treatment on the surface of the foamed resin skeleton having the communication holes. After electroplating, the resin is decomposed and removed by heating (Patent Document 1), and a kneaded product of an organic polymer binder and metal fine bodies is applied to a foamed resin having communication holes by dipping or spraying. After heating, the resin is decomposed and removed, and the metal micro-sinter is sintered (Patent Documents 2 to 4), after the adhesion of the powder to the skeleton surface of the foamed resin having the communicating holes It is manufactured by a method (Patent Document 5) in which the resin is decomposed and removed by heating and the powder is sintered.

  Since the metal porous body having such a three-dimensional network structure has a large contact area with a fluid, application to a heat exchange part of a heat exchanger has been studied (Patent Document 6). A heat exchanger is a device used for heating and cooling applications by efficiently transferring heat from a high-temperature object to a low-temperature object, and generally uses a fluid such as a liquid or a gas as a heat exchange medium. Heating or cooling is performed by applying heat to the fluid (heating) or removing heat from the fluid (cooling). In such a heat exchanger, a fin made of a metal material having high thermal conductivity is provided to increase the contact area with the fluid to increase the efficiency of heat exchange. Instead, if a porous body having a three-dimensional network structure composed of a metal material with high thermal conductivity is used and fluid is passed through the communicating holes, the metal material with high thermal conductivity and the fluid Since the contact area can be further increased, the efficiency of heat exchange is considered to be further increased.

JP-A-57-174484 Japanese Patent Publication No. 61-053417 Japanese Patent Laid-Open No. 08-020831 International Publication No. 2015/046623 Japanese Patent Laid-Open No. 06-235033 Japanese Patent Publication No. 06-089376

The aluminum powder has a strong oxide film (alumina: Al ₂ O ₃ ) on the surface. Therefore, as described in Patent Document 2, a kneaded product of an organic polymer binder and aluminum powder is applied to a foamed resin having communication holes by dipping or spraying, and then heated in a hydrogen stream at 520 ° C. for 2 hours. In the method of decomposing and removing the resin and sintering the metal fine powder, only a small part of the aluminum powder is bonded, and only the brittle and extremely low strength can be produced.

  Further, as in Patent Document 4, after a kneaded product of an organic polymer binder and aluminum or aluminum alloy powder is applied to a foamed resin having communication holes by dipping or spraying, the melting point of the aluminum or aluminum alloy powder is exceeded. In the heating method, when the amount of powder applied is large, molten aluminum or molten aluminum alloy aggregates, and a spherical metal lump is generated non-uniformly on the skeleton. As a result, the pressure loss when the fluid flows through the porous body is increased.

  Accordingly, an object of the present invention is to provide an aluminum-based porous body that can suppress the formation of a spherical metal lump during sintering and reduce the pressure loss of a fluid flowing in the porous body.

  The inventors speculate as follows about "formation of a metal lump" that contributes to deterioration of pressure loss. When the aluminum powder (or aluminum alloy powder) is heated above its melting point, the aluminum melted inside the powder breaks the oxide film and begins to wet the powder surface. However, since molten aluminum has poor wettability with the oxide film, excess molten aluminum aggregates on the powder surface and solidifies upon cooling to form a metal lump. This unevenly formed metal lump exists in the form of a spherical aggregate, suggesting poor wettability between molten aluminum and oxide film, and high surface tension during melting. .

  Based on the above hypothesis, the inventors have repeatedly studied that the surface of the aluminum powder (or aluminum alloy powder) is coated with an anion using an inorganic salt, and the aluminum powder (or aluminum alloy powder) per unit area is coated. It has been found that the formation of metal lumps can be suppressed by setting the adhesion amount to a specific amount. Furthermore, when examining the relationship between the metal mass and the porosity and pressure loss, the major axis of the metal mass was set to a specific size or less, and the porous body having a specific porosity was found to reduce the pressure loss, The present invention has been completed. The “metal lump” described in this specification is a lump shape that is clearly different from the three-dimensionally connected skeleton, and is three-dimensional when viewed from either direction. Unlike a skeleton that is connected in a shape, it means one having a planar spread.

  The present invention is based on these findings, and the aluminum-based porous body of the present invention specifically has a skeleton that is three-dimensionally connected and has pores that are three-dimensionally communicated by the skeleton, In a three-dimensional network structure made of aluminum or aluminum alloy in which aluminum oxide is dispersed inside, the size of the metal block formed on the skeleton is 4 mm or less in the major axis and the porosity is 95. % Or more.

In the aluminum-based porous body of the present invention, the number of metals having a major axis of 1 mm or more and 4 mm or less is preferably 5 or less per 100 cm ² of the surface of the aluminum-based porous body.

Also, the method for producing an aluminum-based porous body of the present invention is a dispersion in which aluminum or aluminum alloy powder is dispersed in a dispersion medium using a continuous pore foamed resin foam as a base, an organic polymer binder, and an inorganic salt. Applying the liquid by immersing or spraying the substrate on the substrate, and heating the substrate after application to the melting point of the aluminum powder or aluminum alloy powder to decompose and remove the substrate and melt the aluminum powder or aluminum alloy powder As a substrate after coating used in the heating step, the adhesion amount of the aluminum powder or the aluminum alloy powder to the apparent volume of 1 L (1000 cm ³ ) of the foamed resin foam is 20 g / L or more and 65 g / L or less. It is what is used.

  In the method for producing an aluminum-based porous body of the present invention, the adhesion amount of aluminum powder or aluminum alloy powder to an apparent volume of 1 L of the foamed resin foam of the base after coating obtained by the coating step is 20 g / L or more and 65 g. The heating step is performed using a substrate after coating having a drawing step of / L or less.

  According to the aluminum porous body of the present invention, it is possible to suppress agglomeration of molten aluminum or a molten aluminum alloy, and therefore, it is possible to provide an aluminum-based porous body having a low pressure loss of a fluid flowing in the porous body. it can. Moreover, the manufacturing method of the aluminum porous body of this invention can manufacture said aluminum porous body easily.

It is a drawing substitute photograph which shows the external appearance of the aluminum porous body in 1st Example of this invention, (a) is a drawing substitute photograph which shows the external appearance of the sample number 2 which is an Example of this invention, (b) is this It is a drawing substitute photograph of the sample number 5 which is a comparative example of invention.

  Hereinafter, the aluminum porous body of this invention and the manufacturing method of this aluminum porous body are demonstrated.

[Aluminum porous body]
The aluminum porous body of the present invention has a three-dimensional network structure having a three-dimensional network structure having a three-dimensionally connected skeleton and a three-dimensional communication hole formed by the skeleton. In such an aluminum porous body having a three-dimensional network structure, a metal lump is easily formed on the skeleton due to a manufacturing method described later. This metal lump is formed on the skeleton by agglomeration of excess molten aluminum or aluminum alloy, and is formed into a spherical shape by surface tension. When such a metal lump is formed coarsely or in a large amount, the pressure of the fluid passing through the communication hole may be blocked by obstructing the flow of the fluid passing through the communication hole or depending on the case. Loss increases.

However, if the size of the metal block formed on such a skeleton is 4 mm or less in the major axis, the pressure loss of the fluid passing through the communication hole can be reduced. Therefore, in the porous aluminum body of the present invention, the size of the metal lump formed on the skeleton is 4 mm or less in the major axis. Further, even if the metal block has a long diameter of 4 mm or less, the number of metal blocks having a long diameter of 1 mm or more is preferably as small as possible. The number of metal blocks having a long diameter of 1 mm or more and 4 mm or less was observed on the surface of the aluminum porous body. Sometimes, it is preferably 5 or less per 100 cm ² of the surface of the aluminum porous body.

  By setting the porosity of the aluminum porous body to 95% or more, the pressure loss of the fluid flowing through the communication holes can be reduced. On the other hand, when the porosity exceeds 98%, the amount of the skeleton is reduced and the strength of the aluminum porous body is lowered. Therefore, the porosity of the aluminum porous body is preferably 98% or less. The porosity can be measured by the method defined in Japanese Industrial Standard (JIS) Z2501.

[Method for producing porous aluminum body]
(Communication hole foamed resin foam)
In the present embodiment, a three-dimensional network structure having a skeleton that is three-dimensionally connected and three-dimensionally connected pores is used as the communicating pore foamed resin foam. This open-pore foamed resin foam is one in which aluminum powder or aluminum alloy powder is deposited and supported on the surface of the skeleton, and decomposes and disappears when heated. Specifically, polyurethane foam is most commonly used, but silicone resin and polyester resin foams can also be used.

(Aluminum powder or aluminum alloy powder)
In the present embodiment, aluminum powder having high thermal conductivity is used as the powder to be attached to the communication hole foamed resin foam. However, instead of aluminum powder, aluminum alloy powder obtained by previously alloying a component that strengthens aluminum may be used. Good. For example, when aluminum alloy powder in which alloying elements such as Cu (copper), Mn (manganese), Mg (magnesium) and Si (silicon) are prealloyed is used for Al (aluminum), an aluminum-based porous body The skeleton is formed of an aluminum alloy, and the strength of the aluminum-based porous body can be improved. By adding alloying elements such as Cu, Mn, Mg, and Si to Al, the thermal conductivity is lower than that of Al alone, but the base metal is Al, so it maintains a sufficiently high thermal conductivity. can do. As the aluminum powder or aluminum alloy powder, a general one, that is, a powder having an oxide film (alumina: Al ₂ O ₃ ) of about 10 mm on the surface is used. Moreover, any one kind of aluminum powder or aluminum alloy powder may be used alone, or two or more kinds may be mixed and used.

In the present embodiment, the aluminum powder or aluminum alloy powder attached to the open pored foam resin foam skeleton is preferably fine because it can be closely attached to the skeleton surface of the open pored foam resin foam. When the powder becomes large, it becomes difficult to adhere closely to the skeleton surface of the continuous pore foamed resin foam, and due to the increase in the mass of the powder, it becomes difficult to adhere to the skeleton surface of the continuous pore foamed resin foam or easily falls off. It becomes. From this viewpoint, it is preferable to use an aluminum powder or an aluminum alloy powder having an average particle diameter of 50 μm or less. Furthermore, it is preferable that the average particle size is 50 μm or less and does not contain powder having a particle size exceeding 100 μm. However, since aluminum is an active metal, too fine powder is difficult to handle. From this viewpoint, it is preferable to use an aluminum powder or an aluminum alloy powder having an average particle diameter of 1 μm or more. The average particle diameter of the present invention is a median diameter (D ₅₀ ), that is, a particle diameter at a cumulative distribution of 50% by volume, and can be measured by a laser diffraction method defined in Japanese Industrial Standard (JIS) 8825.

(Dispersion)
In the present embodiment, the dispersion liquid in which the continuous pore foamed resin foam skeleton is immersed uses a dispersion medium in which aluminum or aluminum alloy powder is dispersed. As the dispersion medium, a liquid in which an organic solvent such as alcohol or water is used as a solvent and an organic polymer binder such as a binder and an inorganic salt are dissolved therein is used. In this case, a dispersant may be added to the dispersion medium so that the powder does not settle. Moreover, as a dispersion medium, you may use the solution of high molecular organic substances, such as a phenol resin.

  As the inorganic salt, for example, phosphate, chromate, sulfate and the like can be used. The surface of the aluminum or aluminum alloy powder is covered with an oxide film, but the anion contained in these salts is adsorbed on the oxide film on the surface of the aluminum or aluminum alloy powder. Thus, the production | generation of a metal lump can be suppressed because an anion coat | covers the powder surface. Also, the viscosity of the dispersion can be changed by changing the ionic species. By adjusting the viscosity, the adhesion amount of the aluminum powder can be accurately controlled, which is preferable in production.

  When water is used as a dispersion medium, it is preferable to add an acid or a base corresponding to the inorganic salt used in addition to the inorganic salt to adjust the pH to 6-8. This is to suppress aluminum corrosion. When aluminum touches water, it becomes aluminum ions and dissolves in water. This dissolution reaction is corrosion. The corrosion rate is fast in acidic and basic aqueous solutions, but relatively slow in neutral aqueous solutions. Examples of the combination of an inorganic salt for providing an anion for coating the powder surface and an acid or base for obtaining a desired pH include those using phosphate as an inorganic salt and sodium hydroxide as a base. It is done.

The addition amount of the inorganic salt is preferably 0.001% by mass or more and 10% by mass or less with respect to the dispersion medium. Furthermore, it is preferable to set it as 0.01 mass% or more and 2 mass% or less. If it is less than 0.001% by mass, the oxide film on the surface of the aluminum or aluminum alloy powder cannot be covered, and if it exceeds 10%, the reaction in which molten aluminum or molten aluminum alloy is mixed and bonded in the subsequent sintering process is inhibited. To do.
(Adhesion process)

  In the present embodiment, the attaching step is a step of attaching a dispersion in which aluminum powder or aluminum alloy powder is dispersed to the open pored resin foam.

  At this time, the aluminum powder or aluminum alloy powder adhering to the surface of the resin skeleton of the substrate can be controlled by the viscosity of the dispersion. That is, when the viscosity of the dispersion liquid is high, the amount of aluminum powder or aluminum alloy powder adhering to the surface of the substrate resin skeleton increases, and conversely, if the dispersion liquid is low, it adheres to the surface of the substrate resin skeleton. The amount of aluminum powder or aluminum alloy powder to be reduced is reduced.

(Amount of adhesion)
In the adhesion step, the adhesion amount of the aluminum powder or the aluminum alloy powder with respect to the apparent volume 1 L (1000 cm ³ ) of the resin skeleton of the substrate is 20 g / L or more and 65 g / L or less. By setting the adhesion amount within this range, it is possible to produce an aluminum porous body in which the size of the metal lump formed on the skeleton is 4 mm or less in major axis. The apparent volume is the volume of the open-hole foamed resin foam including pores. For example, when the shape of the open-hole foamed resin foam is a rectangular parallelepiped, it is the volume of the rectangular parallelepiped multiplied by the width, length, and thickness of the rectangular parallelepiped. . The adhesion amount of the aluminum powder or the aluminum alloy powder is an adhesion amount per unit volume of the aluminum porous body, and the unit volume is an apparent volume of 1000 cm ³ of the continuous pore foamed resin foam.

  That is, the metal lump formed on the skeleton is a spherical lump formed on the skeleton by agglomeration of molten aluminum or aluminum alloy on the powder surface in a heating step described later. Generally, aluminum powder or aluminum alloy powder is known to have a strong oxide film on the powder surface. When a substrate coated with such aluminum powder or aluminum alloy powder is heated to a temperature higher than the melting point of the aluminum powder or aluminum alloy powder, the aluminum or aluminum alloy melted inside the powder breaks the oxide film on the powder surface. As it wets and covers, the molten aluminum or aluminum alloy mixes. However, since aluminum or an aluminum alloy has poor wettability with an oxide film, the molten aluminum or molten aluminum alloy that is in excess of the molten aluminum or molten aluminum alloy necessary for bonding powders agglomerates on the powder surface. As a result, the aggregate is solidified upon cooling and is formed unevenly as a metal lump. Since the aggregate of molten aluminum or molten aluminum alloy becomes spherical due to surface tension, a spherical metal lump is formed on the skeleton.

  In order to reduce such metal lumps, the amount of aluminum powder or aluminum alloy powder to be adhered to the substrate is set as the amount necessary for skeleton formation, that is, bonding between the powders. This can be done by reducing the powder. From this point of view, by setting the adhesion amount of the aluminum powder or aluminum alloy powder to the volume of 1 L of the resin skeleton of the base within the above range, the surplus aluminum powder or aluminum alloy powder is reduced, and the formation of the metal lump is suppressed. The size of the metal lump can be 4 mm or less in the major axis.

  If the adhesion amount of the aluminum powder or aluminum alloy powder with respect to 1 L of the resin skeleton volume of the substrate is less than 20 g / L, only a small part of the aluminum powder or aluminum alloy powder is bonded, and sufficient strength cannot be obtained. On the other hand, when it exceeds 65 g / L, it becomes easy to produce | generate a spherical metal lump. The adhesion amount of the aluminum powder or the aluminum alloy powder liquid can be adjusted by the viscosity of the dispersion liquid and the drawing step described later.

  Here, the adhesion amount of the aluminum powder or the aluminum alloy powder liquid can be calculated as follows. Before adhering the dispersion, the mass of the resin skeleton used is measured and the volume is calculated. After the dispersion is adhered, the mass of (resin skeleton + dispersion) is measured. From this result, the mass of the adhering dispersion is obtained, and the mass of the aluminum powder or aluminum alloy powder adhering to the resin skeleton is calculated from the specific gravity of the dispersion medium and the aluminum powder or aluminum alloy powder. From the result, the adhesion amount of the aluminum powder or the aluminum alloy powder adhered to the volume 1 L of the resin skeleton can be calculated.

(Drawing process)
The amount of adhesion can be adjusted by the viscosity of the dispersion, but the substrate on which the aluminum powder or aluminum alloy powder is excessively adhered together with the dispersion is squeezed, and a part of the aluminum powder or aluminum alloy powder together with the dispersion is removed from the substrate. Adjust by removing. That is, the amount of aluminum powder or aluminum alloy powder removed together with the dispersion can be adjusted by adjusting the squeezing amount, and the amount of aluminum powder or aluminum alloy powder adhering to the substrate after the squeezing step can be freely adjusted. can do.

  In order to carry out such a squeezing process simply, by using an apparatus equipped with a pair of squeezing rolls, a substrate on which aluminum powder or aluminum alloy powder adheres together with the dispersion is passed between the pair of squeezing rolls. The aluminum powder or aluminum alloy powder can be removed from the substrate together with the dispersion. In this case, the amount of aluminum powder or aluminum alloy powder squeezed together with the dispersion can be adjusted by changing the distance between the pair of rolls, and the aluminum powder or aluminum alloy powder adhering to the substrate can be adjusted. . In other words, the amount of aluminum powder or aluminum alloy powder adhering to the surface of the resin skeleton of the substrate can be increased by increasing the distance between the rolls to reduce the amount of drawing, and conversely, the distance between the rolls is decreased. As a result, the amount of drawing can be increased, and the amount of aluminum powder or aluminum alloy powder adhering to the surface of the resin skeleton of the substrate can be reduced. Furthermore, it becomes possible to apply | coat aluminum powder or aluminum alloy powder uniformly to a base | substrate by using the apparatus provided with the roll.

(Drying process)
The substrate obtained by the attaching step or the substrate obtained by the post-drawing step of the attaching step contains a dispersion, and it is preferable to remove the dispersion medium by heating and drying in advance prior to the heating step. The substrate containing the dispersion liquid may be directly subjected to the next heating step without passing through the drying step. In this case, the substrate is heated to the melting point of the aluminum powder or the aluminum alloy powder. In this case, the dispersion medium volatilizes or evaporates in the process of raising the temperature to the melting point of the aluminum powder or aluminum alloy powder, which may contaminate the atmosphere in the furnace. Therefore, when the substrate containing such a dispersion is directly subjected to the next heating step, it is necessary to take measures so that the volatilized or evaporated dispersion medium is quickly discharged out of the furnace. In other words, if a heating device with such measures is used, the substrate containing the dispersion may be directly used in the next heating step.

(Heating process)
As described above, the continuous-hole foamed resin foam (substrate) adhered to the surface of the skeleton by adjusting the adhesion amount of the aluminum powder or aluminum alloy powder is the melting point of the aluminum powder or aluminum alloy powder in a non-oxidizing atmosphere. It is heated above. In the process of raising the temperature up to this melting point, the binder component and the resin-made communicating hole foamed resin foam are decomposed and removed to disappear.

When the heating temperature exceeds the melting point of aluminum (melting point: 660.4 ° C.) or aluminum alloy, the aluminum powder or aluminum alloy powder melts inside. That is, the surface of the aluminum powder or aluminum alloy powder is covered with an oxide film (alumina: Al ₂ O ₃ ), and the melting point of alumina is as high as 2072 ° C., so the oxide film on the surface of the aluminum powder or aluminum alloy powder melts. The inside of these powders melts. The aluminum or aluminum alloy thus melted inside breaks the oxide film on the surface of the powder and wets and covers the powder surface, and the molten aluminum or aluminum alloy is mixed. The oxide film formed on the powder surface is dispersed in molten aluminum or molten aluminum alloy generated from each powder. The oxide film serves as a substitute skeleton, maintains the shape of the skeleton, and the surface tension of molten aluminum or molten aluminum alloy bonded to each other makes the skeleton surface relatively smooth and the neck portion disappears to become a continuous metal surface. As a result, the density ratio inside the skeleton of the three-dimensional network structure is 90% or more, and the strength of the skeleton is high and the thermal conductivity is high.

  On the other hand, when the heating temperature is lower than the melting point of aluminum or aluminum alloy, a strong oxide film formed on the surface of aluminum powder or aluminum alloy powder becomes a barrier, and diffusion between aluminum powders or aluminum alloy powders Sintering does not proceed due to hindering the joining.

When the atmosphere in the heating process is an oxidizing atmosphere such as air, the molten aluminum or molten aluminum alloy exposed by breaking the oxide film on the powder surface is immediately oxidized, and the molten surface generated by wetting or covering the powder surface. Mixing of aluminum or molten aluminum alloy is prevented, and bonding between the powders is hindered. For this reason, it is desirable that the atmosphere in the heating step be a non-oxidizing atmosphere such as nitrogen gas or inert gas. The above heating step is not intended to remove the oxide film on the surface of the aluminum powder or aluminum alloy powder, so it is not necessary to be in a reducing atmosphere such as hydrogen gas or a hydrogen mixed gas. Since this atmosphere is a non-oxidizing atmosphere, it may be a reducing atmosphere. Moreover, it is good also as a pressure-reduced atmosphere (vacuum atmosphere) whose pressure is 10 < ^-3 > Pa or less.

  In addition, the powder can be melted if the heating temperature exceeds the melting point of the aluminum powder or aluminum alloy powder adhered to the continuous pore foamed resin foam. However, heating at a temperature greatly exceeding the melting point requires extra energy. At the same time, the viscosity of the molten aluminum or aluminum alloy is lowered, and the mold tends to be deformed. Moreover, molten aluminum or a molten aluminum alloy is aggregated and a metal lump is easily generated. Therefore, the heating temperature is preferably up to the melting point + 100 ° C.

  When pure aluminum powder is used, the obtained aluminum-based porous body is Al: 95% by mass or more and the balance is made of impurities such as C, N, O, etc., and does not contain other metal elements.

  In addition, when an aluminum-based porous body is composed of an aluminum alloy, components (Cu, Mg, etc.) that generate a eutectic liquid phase with Al are added to the aluminum powder as a simple powder or an aluminum alloy powder. A method of using an aluminum-based mixed powder, attaching the aluminum-based mixed powder to the surface of a resin substrate having a three-dimensional network structure, and sintering at a temperature at which a eutectic liquid phase is generated can be considered. Then, the distribution of the component elements in the aluminum-based porous body is not uniform. On the other hand, by using the aluminum prealloy powder in which the component elements are prealloyed in Al as described above, the distribution of the component elements in the aluminum-based porous body becomes uniform, and high strength and thermal conductivity are obtained. Can be obtained.

  When the porous aluminum body produced as described above is produced by heating to a melting point or higher using a continuous pore foamed resin foam (substrate) in which aluminum powder or aluminum alloy powder is adhered to the surface of the skeleton, The excess aluminum powder or aluminum alloy powder was removed by adjusting the adhesion amount of aluminum powder or aluminum alloy powder, so that the size of the metal lump formed on the skeleton became 4 mm or less in the major axis, and the pressure loss was small It becomes an aluminum porous body.

[First embodiment]
A polyurethane foam having a length of 100 mm, a width of 100 mm, and a thickness of 25 mm was prepared as a resin base having a three-dimensional network structure. This polyurethane foam had a porosity (ratio of the volume of communication holes to the total volume) of 95%, and the size of the communication holes was 20 ppi.

  Next, a dispersion medium was prepared. Polyvinyl alcohol (Wako Pure Chemical Industries) was used as the organic polymer binder, and sodium phosphate (Wako Pure Chemical Industries) was used as the inorganic salt. Sodium phosphate was dissolved in pure water, and sodium hydroxide (Wako Pure Chemical Industries) was added to adjust the pH to 6.8. It added to the dispersion medium so that the density | concentration of sodium phosphate might be 0.5 mass% with respect to a dispersion medium. As a comparative example, a dispersion medium to which sodium phosphate and sodium hydroxide were not added was also prepared. Aluminum powder having an average particle diameter of 6 μm was mixed with the prepared dispersion medium to prepare an aluminum powder dispersion having an aluminum powder: dispersion medium mass ratio of 5: 3.

  The prepared substrate was immersed in the prepared aluminum powder dispersion, and the excess dispersion impregnated in the substrate was removed using an apparatus equipped with a pair of squeezing rolls. At this time, six types of substrates were produced in which the amount of aluminum powder adhered to a 1 L volume of the substrate was changed in the range of 17.8 to 70.6 g / L.

  The adhesion amount is determined by measuring the mass of the resin skeleton before adhering the dispersion liquid, measuring the mass after the squeezing step with a roll, and determining the mass of the dispersion liquid adhering to the substrate, and calculating the specific gravity of the dispersion medium and the aluminum powder. From this, the mass of the aluminum powder adhering to the resin skeleton was calculated, and the amount of the aluminum powder adhering to the volume of 1 L was calculated.

The substrate after passing through the roll was dried at 80 ° C. for 60 minutes, and then heated at 665 ° C. for 210 minutes under a reduced pressure atmosphere (vacuum atmosphere) with a pressure of 10 ⁻³ Pa to produce a porous aluminum sample. did.

  The porosity of the aluminum porous body sample produced as described above was calculated, and the number of metal lumps produced on the outer surface was counted visually.

  Moreover, the pressure loss was measured about these samples. The pressure loss is 50 mm in length and 50 mm in width at the exit of the wind tunnel that can blow a constant air volume, and an acrylic tube with a length of 300 mm is attached, and 50 mm in length on the side opposite to the wind tunnel side of this acrylic tube. A device having an aluminum porous body sample cut to a size of 50 mm in width and 10 mm in thickness attached thereto is blown with a constant amount of air (surface velocity 1 m / s) from the wind tunnel, and the end face of the aluminum-based porous body It was calculated by measuring the pressure on the wind tunnel side and the opposite side.

  Table 1 shows the adhesion amount, porosity, number of metal lumps exceeding 4 mm in major axis, number of metal lumps having a major axis of 1 to 4 mm, and pressure loss. In Table 1, numerical values deviating from the scope of the present invention are underlined.

  Sample No. 1 in which the adhesion amount of the aluminum powder was less than 20 g / L could not maintain the skeletal structure because the bonding between the powders was weak.

  Sample Nos. 2 to 5 having an adhesion amount of aluminum powder of 20 g / L or more and 65 g / L all had a porosity of 95.0% or more. Among these, Sample Nos. 2 and 5 using an inorganic salt did not produce a metal block having a major axis of 1 mm or more. The appearance of the sample of sample number 5 is shown in FIG. FIG. 1A shows a good appearance with no metal lump.

  On the other hand, Sample Nos. 3 and 4 in which no inorganic salt was used produced a metal lump. The appearance of the sample of sample number 3 is shown in FIG. In FIG. 1B, a substantially spherical mass is recognized in the sample. In FIG. 1B, the portion surrounded by a solid circle is a metal lump exceeding 4 mm, and the portion surrounded by a broken circle is a metal lump of 1 to 4 mm. Thus, it is recognized that the sample of sample number 3 has a metal lump exceeding 4 mm.

  Sample No. 6 in which the adhesion amount of the aluminum powder exceeded 65.0 g / L had a porosity after sintering of less than 95.0%, and a metal lump was generated.

  Comparing the pressure loss, Sample Nos. 2 and 5 using inorganic salts had a pressure loss of less than 1.0 kPa / m. On the other hand, the pressure loss of Sample Nos. 3 and 4 in which no additive was used was 1.0 or more. From the above, it was suggested that an aluminum-based porous body having a uniform skeleton structure can be obtained by adding an inorganic salt.

[Second Embodiment]
Next, the influence of the kind of inorganic salt on the aluminum porous body was investigated. The examined inorganic salts are shown in Table 2. A sodium salt having excellent water solubility was examined among ammonium salts, alkali metal salts, alkaline earth metal salts, and the like. Each of these salts was dissolved in pure water, and sodium hydroxide was added to adjust the pH to 6-8.

  Any of sulfate, chromate, and phosphate can produce porous aluminum without forming a metal lump, but sulfate is prone to corrosion from the coating process to the drying process. I found out there was a problem. There was no apparent difference in appearance between chromate and phosphate, but considering that the raw material chromate (sodium dichromate) is a deleterious substance, those using phosphate It can be said that it is preferable in terms of the environment. Moreover, although any inorganic salt was used, the amount of powder falling tended to increase somewhat as the amount added increased. However, this was not a level that impairs the porous structure, and it was determined that there was no problem in practical use.

  The aluminum-based porous body of the present invention is suitable for use in various porous members because it has few spherical metal blocks and low pressure loss.

Claims (4)

In a three-dimensional network structure having a skeleton that is three-dimensionally connected and having pores that are three-dimensionally communicated by the skeleton, the skeleton being made of aluminum or an aluminum alloy in which aluminum oxide is dispersed.
An aluminum-based porous body in which a metal lump formed on the skeleton has a major axis of 4 mm or less and a porosity of 95% or more. The aluminum-based porous body according to claim 1, wherein the number of metal lumps having a major axis of 1 mm or more and 4 mm or less is 5 or less per 100 cm ² of the surface of the aluminum-based porous body. An application process in which a dispersion liquid in which aluminum or aluminum alloy powder is dispersed in a dispersion medium to which an organic polymer binder and an inorganic salt are added is immersed in and applied to the base using a continuous pore foamed resin foam as a base, is applied excessively Squeezing process to remove the dispersed liquid,
Heating the substrate after coating to the melting point of the aluminum powder or aluminum alloy powder to decompose and remove the substrate and melting the aluminum powder or aluminum alloy powder;
Aluminum base using a base body in which the adhesion amount of aluminum powder or aluminum alloy powder liquid to an apparent volume of 1 L (1000 cm ³ ) of the foamed resin foam is 20 g / L or more and 65 g / L or less is used as the base after coating used in the heating step. A method for producing a porous body.   The squeezing step was carried out so that the adhesion amount of the aluminum powder or aluminum alloy powder to the apparent volume of 1 L of the foamed resin foam of the base after coating obtained by the coating step was 20 g / L or more and 65 g / L or less. The manufacturing method of the aluminum-type porous body of Claim 3 which performs the said heating process using the base | substrate after application | coating.

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